I'm 21 years old I weigh aprox 200 lbs I get my period every 27-30 days my husband and I have been trying for 4 years and nothing I don't understand why its not happening for us

So what have you done up to this point?
Have you both been checked by your doctors for any sexual issues for pregnancy?

I would assume you are tracking your fertile times and not having sex in unproductive times and only having sex during the best chance times?

Your only 21 it will happen when it is time. However if you really want this to be then you can try a few things. After you both have been together try to keep your bottom elevated in the air, try standing on your head. I know this sounds strange put it has been proven to work, this help the little guys get to where the eggs are a lot quicker then normal and prevents them guys from falling out.

In order to become pregnant, a sperm must meet and fertilize an egg. An egg is only available for fertilization for about a 12-24 hour window each month – this is known as ovulation. Predicting ovulation can help you to figure out when you are most fertile and when are the certain times to be careful.

If a female engages in intercourse around the time that she is ovulating, she is more likely to get pregnant. Therefore, if a couple is having unprotected intercourse, they should be most “careful” during the 5 days leading up to ovulation and the 1 day (24 hours) after it. This is because sperm can live inside the female body for up to 5 days, so even if a woman does not ovulate for another 4 days after having sex, there could still be sperm living inside of her that can fertilize the egg when it is released.

Timing ovulation can be tricky as it may not always happen at the same time each month. When people try to avoid pregnancy by figuring out when they are most fertile, this is known as the fertility awareness method of birth control.

In general, research has shown that for most women who consistently have periods every 26-32 days, conception is most likely to occur during days 8-19. When counting the days of a menstrual cycle, a woman should count the day that her period starts as Day 1. Don't go to the bathroom right after intercourse!

To get pregnant faster have enjoyable sex.
Sometimes when couples are trying to conceive, sex becomes a job or function of reproduction and is not as enjoyable. Plan a romantic evening or try something different to spice things up. How you are feeling sexually may factor into your chances of getting pregnant. Some researchers believe that having an orgasm during sex increases your chances of getting pregnant. For women, the spasmic movements of orgasm will help pull the sperm into the uterus and for men a better orgasm may increase the man's sperm count.

Have sex in positions that keep sperm inside the vagina longer.
The missionary position is a good position to use when trying to get pregnant. Avoid positions where the woman is on top. Gravity will allow sperm to leak out with these positions. Also try placing a pillow under your hips to help tilt your pelvis and keep the sperm in longer. Don't get up right after sex. Try to relax and allow the sperm to stay in the vagina as long as possible.

To get pregnant faster have sex three or more times a week.
Having regular sex is the best way to get pregnant right away. Couples often try to time everything perfectly for ovulation but do not have sex when they think they are not ovulating. It is true that sex that is not within the time of ovulation will not result in pregnancy. However, because women do not always ovulate when they think they will, having sex three or more times a week will help a woman to cover her bases, so to speak, and not miss an opportunity to get pregnant.

I hope this helps there are many different website out there with more information for you to read up on. But I believe I have covered all the bases for you here. Good luck and best wishes.